Preparing Masonry Surfaces

Masonry surfaces suffer some of the same categorical damage as other surfaces. They often display cracks or damages that require patching.

Patching damaged masonry can prove more difficult than repairing wood siding because even the best masonry repairs are visible, if only slightly. Although it's almost impossible to match the texture and color, getting a tight seal between the patch and the original surface is what really matters. Cracks and holes in stucco let water into the walls and will cause problems far worse than a mismatched patch.

When pigmenting a stucco patch, take the time to experiment with pigment proportions until you find a tint that matches the existing stucco when the patch dries.

Make necessary repairs to the underlying structure before you begin. Plan on building up your repair in layers over several days, allowing the patch to cure between applications. Thick applications will crack.

If the surface of the brick is actually flaking off, the best solution is to skimcoat the entire wall with a portland-cement mortar. If it's just the mortar joints that show serious deterioration, rake out the loose mortar with a raking tool, remove the dust, and tuckpoint them.

Flaking brick doesn't necessarily indicate a structural deficiency but does pose an aesthetic problem. Once flaking begins, it is almost certain to continue, even if you paint the brick. The best solution is to apply a skimcoat of mortar over the entire surface. Let it cure, then paint.

Repairing masonry mortar joints: Step 2

Small cracks can be enlarged and filled with a masonry-repair patching compound. Whatever kind of repair you make, be sure to smooth the joints with a masonry jointing tool so the contours of the repaired joints match those of the old.

Narrow cracks in concrete block (less than 1/4 inch wide) can be filled with caulking made specifically for this purpose or painted with an elastomeric wall covering. Both products expand and contract with the block, effectively bridging the crack, and both can be painted.

Wider cracks in concrete block should be keyed (made wider at the bottom of the crack than at the surface) with a cold chisel. This helps them hold the patching mortar more effectively. Remove residual dust with a brush or vacuum.

Using a pointed trowel, narrow putty knife, or margin trowel, apply a thin coat of stucco patch and let it dry. Apply two more layers in the same fashion until the patch is level with the surrounding area. Do not let this coat dry before going to step 3.